The present invention relates to a valve device, comprising a housing with an inlet and an outlet to be connected to an exhaust conduit in an internal combustion engine, an exhaust passage disposed between the inlet and outlet, a valve body which can be set in various positions to vary the throughflow area of the exhaust passage, and operating means for setting the valve body.
It is known that it is possible by merely increasing the exhaust counterpressure in the exhaust conduit of an internal combustion engine, with the aid of a valve device of the above mentioned type, to achieve an increase in the engine braking effect of the vehicle. A further increase in the engine braking effect can be achieved if communication is established in a known manner between the exhaust system and the engine cylinders during the latter portion of the intake stroke, so that gas from the exhaust system can flow into the cylinders. This results in a pressure increase in the cylinder, and an inner charging pressure which increases the compression work after cutting off the communication between the cylinders and the exhaust system.
A known type of valve device for varying the exhaust counterpressure is an exhaust pressure regulator comprising a damper in the exhaust conduit. Great demands are placed on the design of damper valves which must be able to function with high reliability and lone life in the exhaust conduit environment. They must be able to withstand high mechanical and thermal stresses. In the open position, they must not provide any flow impediment or create turbulence in the exhaust conduit, and they must not stick so that they do not reach their defined positions, something which often happens after a relatively short operating period due to deposits of soot.